The present invention relates generally to liquid crystal displays and more particularly to a method for fabricating the backplate for such displays having thereon spacers to maintain the thickness of the liquid crystal display uniform throughout.
In copending application Ser. No. 352,397 filed by Hans G. Dill et al. on Apr. 18, 1973, and entitled Liquid Crystal Display System with Integrated Signal Storage Circuitry, there is described a liquid crystal display panel having a plurality of spacers between the back and front panels of the liquid crystal display. The purpose of these spacers is to maintain a uniform spacing between the front and back panels of the liquid crystal display. One of the features of the invention described in the referenced application is the provision of addressing circuitry which is fabricated in the back panel of the display, which for this purpose is a semiconducting wafer.
It is a principal object of the present invention to provide a method for the fabrication of spacers of the type disclosed in the referenced patent application which method is compatible with the steps required to fabricate liquid display panels of the type therein described.
It is a related object of the invention to provide a method for the fabrication of back panels for liquid crystal displays with spacers which are accurately located with respect to an array of electrodes, also on the back panel.
A further object of the present invention is to provide a method for fabricating liquid crystal display back panels with integral spacers thereon wherein the spacers are resistant to attack by the liquid crystal material, and may serve to shield electrically conductors that run to the electrodes.
In accordance with the invention the above and other objects are accomplished by first forming an array of reflective electrodes in spaced apart columns and rows on a surface of a substrate panel which is preferably a semiconducting wafer. This step may be preceded by several steps directed to the formation of a plurality of switching devices in the surface of the semiconducting substrate as described in the referenced patent application. Following the formation of the reflective electrodes there is deposited a layer of insulating material, preferably oxide, on top of the substrate surface and over the electrodes, after which an additional layer, preferably of aluminum, is deposited over the layer of insulating material. A two-layered spacer lattice is formed from the successively deposited layers by removing those portions of the layers which are over the central portions of the electrodes. Preferably, so much of the layers is removed as to expose all but the extreme perimeters of the array of electrodes, thereby providing a slight overlap of the two-layered lattice over the electrodes. The resulting structure, comprising the back panel having a plurality of electrodes on its surface and a spacer lattice extending integrally from that surface, may then be used to complete the fabrication of a liquid crystal display by adding a front transparent panel having a transparent electrode thereon and placing a nematic liquid crystal material between the front and back panels.